In the process of continuously casting metal strips, such as ribbons, it is common practice to dispense molten metal through an elongated slot of a dispensing nozzle onto a relatively moving chilled surface positioned immediately adjacent the elongated slot. The molten metal solidifies soon after contact with the chilled surface. A relatively thin elongated strip or ribbon having an amorphous molecular structure cast in this manner has proven to be effective for winding into highly efficient cores for electrical transformers, and other uses. Recent developments in the casting of amorphous metal strips are reviewed in U.S. Pat. No. 4,142,571.
A conventional nozzle for depositing molten metal ribbons in a continuous casting operation has a body formed of ceramic material. The nozzle body has a relatively large opening on one side for receiving molten metal from a crucible. This relatively large opening extends into a hollow interior melt chamber in the nozzle, which melt chamber converges into a relatively narrow elongated dispensing slot.
Considerable difficulties have been experienced in the past in providing elongated dispensing slots of consistent dimension. Moreover, due to the fact that the nozzles are frequently formed of ceramic material, the dispensing slots have been formed by relatively expensive methods, such as diamond wheel cutting, laser cutting or ultrasonic cutting. Many of these techniques have resulted in irregular surfaces on the longitudinal ends of the slots. Consequently, it is commonly necessary to manually file and square off the longitudinal ends of the dispensing slots.
Further, the width of cast ribbons dispensed through such nozzles is generally a function of the longitudinal dimension of the slot in the nozzle. In the past, it was necessary to determine the slot width at the cutting state, each desired ribbon width being formed by a slot of corresponding slot length. Thus, once the slot was cut, the nozzle became dedicated for producing a single ribbon width.
The ends of the longitudinal dispensing slots in prior art nozzles have also been subject to stress concentrations. Cracks tend to originate in these areas of stress concentration and propagate throughout the nozzle, resulting in nozzle failure. Hence, a substantial need existed for reducing both the formation and propagation of stress cracks.
It has also been known to provide relatively expensive casting surfaces having lateral dams to confine and limit the width of the cast ribbon. In U.S. Pat. No. 3,228,072 for example, a plurality of small blocks of hard, heat resistant metal are strung in end to end relationship on lateral sides of a continuously moving casting surface of an endless belt. The laterally disposed dams are adjustable to produce cast strips of different widths.
In U.S. Pat. No. 1,600,688, the thickness of a cast metal sheet is determined by a gasket or plate. This last mentioned patent teaches that the plate for guaging the thickness of the cast sheet may either extend beyond the ends of the casting slot or close portions of that slot to alter the shape of the cast metal.